1. Technical Field
This disclosure relates to a gateway apparatus including gateway functions that conform to the ITU-T recommendation T.38, and relates to a network terminal apparatus including terminal functions that conform to the ITU-T recommendation T.38, wherein the gateway apparatus is connected to both of an analog public network and an IP network, and the network terminal apparatus is connected to an IP network.
2. Description of the Related Art
Recently, a communication apparatus that conforms to the ITU-T recommendation T.38 has been brought into practical use for realizing facsimile communications by using the IP network such as the Internet as a relay network. Japanese laid-open patent application No. 2001-292267 discloses this technology.
For example, the gateway apparatus that includes communication functions conforming to the recommendation T.38 is connected to both of the analog public network and the IP network, and the gateway apparatus provides gateway functions to each of a group 3 facsimile apparatus in a sending side and a group 3 facsimile apparatus in a receiving side.
In a communication system using such a gateway apparatus, for example, the group 3 facsimile apparatus in the sending side originates a call to a first gateway apparatus via an analog public network, and sends a facsimile number of a destination group 3 facsimile apparatus to the first gateway apparatus. Then, the first gateway apparatus connects to a second gateway corresponding to the destination facsimile number via the IP network so as to send the destination facsimile number to the second gateway. Then, the second gateway originates a call to the destination group 3 facsimile apparatus corresponding to the specified facsimile number.
Accordingly, a communication path is established between the group 3 facsimile apparatus in the sending side and the group 3 facsimile apparatus in the receiving side via the analog public network, the first gateway apparatus, the IP network, the second gateway apparatus and the analog public network. By using the communication path, predetermined facsimile communication operations are performed between the group 3 facsimile apparatus in the sending side and the group 3 facsimile apparatus in the receiving side.
In such a communication system, if the distance between the group 3 facsimile apparatus in the sending side and the group 3 facsimile apparatus in the receiving side are long, there is a merit that communication cost can be reduced since the IP network is used as a relay network.
In addition, in a situation in which VoIP (Voice over IP) communications become widespread in recent years, the communication cost can be further reduced since the IP network being used for the VoIP can be used for facsimile communications as it is.
In the above-mentioned communication system, if makers of the group 3 facsimile apparatus in the sending and the group 3 facsimile apparatus in receiving sides are the same, the communication system can be controlled such that facsimile communications can be performed more efficiently by using maker-specific features. In this case, so-called maker-specific mode (also to be referred to as “non-standard mode”) can be utilized.
That is, compared to standard communication functions provided by the ITU-T recommendation T.30 that defines the group 3 facsimile communication procedure, the better performance can be obtained by using the maker-specific optional functions. For example, a communication time can be reduced and a higher quality image can be obtained by using the maker-specific optional functions.
Signals used for negotiations for the optional functions in facsimile transmission control procedure signals are signals that can set optional functions, which are, for example, NSF, NSC and NSS.
Mapping information in information fields in the signals that define the optional functions is maker-specific, and is not disclosed to other makers.
Therefore, if a maker of a gateway apparatus connected to a group 3 facsimile apparatus is different from a maker of the group 3 facsimile apparatus, the gateway apparatus can not interpret information in information fields in the signals NSF, NSC and NSS transmitted by the group 3 facsimile apparatus. Therefore, for example, the gateway apparatus cannot detect a communication speed determined between the sending side and the receiving side. As a result, a communication error occurs in a stage in which image information is sent and received (phase C in the group 3 facsimile transmission procedure), so that the communication path is disconnected.